Terms such as radiotelephone, radiotelephone terminal, or mobile terminal, generally refer to communication terminals which provide a wireless communication link to a network, and thus to other radiotelephone terminals. This terminology most readily conjures images of “cellular” type mobile phones. However, the terminology may refer to radio terminals that are used in a variety of different applications, including land mobile, and satellite communication systems. Radiotelephone terminals typically include an antenna for transmitting and receiving wireless communication signals. Historically, monopole and dipole antennas have been employed in various radiotelephone terminal applications due to their simplicity, wide band response, broad radiation pattern, and low cost.
Miniaturization of the electronics for such terminals has increased interest in small antennas that can be internally mounted for use in radiotelephone terminals. Once such type of antenna is the planar, inverted-F antenna (PIFA) such as that illustrated in FIG. 1. In FIG. 1, illustrated antenna 100 includes linear conductive element 102 maintained in a spaced apart relationship with ground plane 104. Conventional inverted-F antennas, such as that illustrated in FIG. 1 derive their name from their resemblance to the letter “F”. In FIG. 1, illustrated conductive element 102 is connected to the ground plane 104 as indicated at 106. A signal feed connection, 107, extends from underlying radio frequency circuitry through ground plane 104 to conductive element 102. An antenna like that illustrated in FIG. 1 typically resonates at a specific, narrow, frequency band. The resonance frequency of a PIFA can be broadened through the use of non-linear conductive elements. In such cases, the element is bent, curved, or formed, in some cases to meet the contours of the housing in which it is installed. By adjusting the width and length of the various segments of a non-linear conductive element, the resonance frequency of the antenna can be broadened and adjusted.
It should be noted that it has also become desirable for radiotelephone terminals to be able to operate within multiple frequency bands in order to use more than one communication network. For example GSM (Global System for Mobile) is a digital radiotelephone system that operates from 880 MHz to 960 MHz in many countries, at 1,710 MHz to 1,880 MHz in still other countries, and at 1,850 MHz to 1,990 MHz in still other countries. Multi-band operation for a non-linear, planar inverted-F antenna can be achieved for such systems by making the resonance frequencies broad, and by forming a radiating branch from segments that cause the antenna to radiate efficiently in at least two, broad bands. However, if there is a desire to add additional frequency bands, it is usually necessary to add an additional antenna. This may be the case when it is desirable to combine a radiotelephone terminal with global positioning system (GPS) function, wherein the GPS frequency is approximately 1,575 MHz. Another example would be the case where (Bluetooth) short range wireless functionality is desired. Bluetooth operates at approximately 2,400 MHz. In the current art, GPS or Bluetooth functionality typically requires an additional antenna.